Zaštita materijala 2009

Broj 1

Inhibitive action of some 3-thiazinonyl-bicyclo[4.2.0] octene-carboxylate derivatives drugs on the corrosion of SS type 304 in 1M HCl solution

The effect of 3-Thiazinonyl-bicyclo[4.2.0]octene-carboxylate derivatives drugs on the corrosion behavior of 304 stainless steel in 1.0 M hydrochloric acid solution as corrosive medium has been investigated using weight loss and potentiostatic polarization techniques. Some corrosion parameters such as anodic and cathodic Tafel slope, corrosion potential, corrosion current, surface coverage and inhibition efficiency were calculated. The polarization measurements indicated that the inhibitors are of anodic type and inhibit corrosion by adsorption on the surface of steel due to the presence of more than one active centre in the inhibitor molecule. The adsorption is obeyed Langmuir adsorption isotherm. The activation energy and thermodynamic parameters were calculated in the temperature range 25–55oC. its found that The corrosion rate increases with temperature and the inhibition efficiency decreases with increasing temperature.

Electrocoagulation is a greener and cheaper method to remove Cr(VI) form the effluents of electroplating industry. This paper is emphasizing on the removal efficiency of electrocoagulation method. The removal efficiencies (R) of chromium after 15 min of electrolysis at 0.8 A, reached value as high as 99.9%, when pH just 4, and maintain the same efficiency up to pH 8. The treatment rate is found to increase upon in­creasing the current density. Indeed, the optimum current pro­duced the quickest treatment with an effective reduction of Cr (VI) concentrations in the industrial wastewater below permissible level within 20 min. When comparing the electrodes, iron electrodes more efficient to remove chromium comparing the aluminum and hybrid Al/Fe electrodes.

ELECTROCHEMICAL BEHAVIOR OF Cu24Zn5Al ALLOY IN BORAX BUFFER SOLUTION IN THE PRESENCE OF 1-PHENYL-5-MERCAPTO TETRAZOLE

The results of investigation of the effect of 1-phenyl-5-mercapto tetrazole (PMT) on electro­chemical behavior of Cu24Zn5Al alloy in borax solutions, are presented in this paper. The pola­rization measurements were conducted in 0,1 mol/dm3 borax solutions containing various concetrations (1·10-6 mol/dm3÷1·10-2 mol/dm3) of 1-phenyl-5-mercapto tetrazole, as well as after electrode exposure (5, 15 and 60 min) in PMT solution. 1-phenyl-5-mercapto tetrazole was found to indicates better inhibition effect when Cu24Zn5Al electrode was previosly immersed in a PMT solution. Also, the polarization measurements were performed in borax solution containing various concentrations (1·10-4 mol/dm3÷5·10-2 mol/dm3) of chloride ions, with (15 min) and wit­hout previous immersion of electrode in PMT solution. The high values of chloride ions con­cetrations decrease of the electrode surface coverage degree. Results show that 1-phenyl-5-mercapto tetrazole was adsorbed on the electrode surface according to the Lengmuir adsorption isotherm.

Characterization of electrochemically synthesized PANI on graphite electrode for potential use in electrochemical power sources

Polyaniline (PANI) on graphite electrode was synthesized electrochemically under galvanostatic condition at current density of 2.0 mA cm-2 from aqueous solution of 1.0 moldm-3 HCl and 0.25 mol dm-3 aniline monomer. Electrochemical characterization of the PANI electrode was performed in 0.5 mol dm-3 HCl using cyclic voltammetry and galvanostatic measurements. The overall charge capacity of the PANI electrode was estimated to be 0.154 mA h cm-2, which corresponds to 25% of the theoretical mass of PANI available for doping exchange. It was observed that during initial cyclization at low pH, the extent of PANI degradation products was insigni.cant and practically had no infuence on the charge/discharge characteristics of the PANI electrode.

DETECTION AND DETERMINATION SOME HEAVY METALS IN WATER PRESENT IN THE WATER.SUMPPLY SYSTEM OF THE BELGRADE – CONDUIT PART VIDIKOVAC ON THE BASIS OF HOUSE WATER HEATER ORIGINATED SCALE

The aim of this paper is to analyze scale made from heating drinking water from Belgrade conduit part Vidikovac. The major component of fur (boiler scale) is calcium carbonate, but also there are some other alkali and alkaline (earth) metals (88.35 %) heavy metals (10.71 %), radioactive elements: uranium in concentration of 1,5 ppm or 0.0003 %. There are found in scale and according to that they are in drinking tap water.

In test drinking water determined presence of some elements, witch if they are presence in higher concentration in drinking water could cause accumulation effect (for example Hg, Pb). There were detected some elements like Ni, As which haven’t been found in arms of Belgrade conduit till now by this method. That shows domain of highly industrial production.

For that propose was used for the first time method fractional extraction, was determined that uranium associated mostly with oxides: manganese and iron (74.34 %) totally 98.02 % for the present state potential accessible to humans. This means that in drinking water are natural uranium and uranium in environment made by people.

Conditions for obtaining copper powder with different regimes of electrolysis [potentiostatic, galvanostatic and programmed current-voltage regimes ( periodically changing rate)] and effects on it’s morphology and characterization have been subject of reaserch for a long period of time. In addition to used regime of electrolysis, there is quantified criteria which connect shape and size of particles and decesive properties of powder, in laboratory as well as in pilot plant scale. Applying together stereological parmeters with elementary statististic parameters (quantitative microscopical analysis) and scanning electron microscopy, enables successfully obtained shape, size of each particle as well as their distribution. However, the processes of obtaining powder and it’s characterization are just one phase. In case of obtaining cupric oxide powder by electrolysis, it is necessary for processed powder to convert to CuO, with controlled technological process, throughout several phases: washing out, centrifugion, drying, oxidation, airseparation, sieving, grinding and homogenization.

CORROSION CAUSES IN THERMAL POWER PLANTS AND WAYS OF PREVENTION

Corrosion damages often exert consiredable influence on outages number and hence on the loss of thermal power plant availability. In order to accomplish the aim of reducing the corrosion to it’s mi­nimum and prevent main thermal power plant corrosion, particularly of steam boilers, it is important to determine corrosion mechanisms and main causes in each particular case. The paper presents cor­rosion’s basics and its various types, the materials used for steam boilers and other parts of thermal power plants. Special attention is given to water preparation, in consideration of its significance for corrosion. There is given general review of corrosion types in thermal power plant facilities also. There were also elaborated corrosion damages of boiler tubing system in TPP ”Ugljevik”. Main ca­uses of corrosion damages have been discovered with recommendations for its reduction.

SOME ASPECT OF STEEL DISSOLUTION IN HYDROCHLORIC ACID

The paper show experimental result of etching steel in hydrochloric acid with and without oxide. Change of steel acid etching rate with and without inhibitor are show. The kinetic and mehanizm of steel eaching in function of time and themperature are show.

The one of most common methods of applying zinc metal to iron and steel for corrosion protection are Hot-Dip Galvanizing process. Development of hot-dip galvanizing realized through development pretreatment, with addition of different alloying elements in minimum
98 % pure molten zinc and post treatment zinc coatings. The hot-dip galvanizing coating is resulting in a metallurgical bond between zinc and steel with a series of distinct iron-zinc alloys.

An aqueous extract of plant material Henna (Lawsonia Inermis L) powder has been used as a corrosion inhibitor in controlling corrosion of carbon steel immersed in an aqueous solution containing 60 ppm of Cl–, by the mass loss method, in the absence and presence of Zn2+. The main constituent of this plant extract is Lawsone. It has excellent inhibition efficiency (IE) and shows excellent IE at pH 6, 8 and 12. In the presence of Zn2+ there exists a synergistic effect. Synergism parameters have been calculated to evaluate the synergistic effect. Analysis of variance (F-test) reveals that the synergistic effect existing between henna extract and Zn2+ in statistically significant. The protective film has been analyzed using Fourier transform infrared (FTIR) spectroscopy. The film consists of Fe2+ – Lawsone complex and Zinc hydroxide [Zn (OH)2]. It is found to be UV-fluorescent. Electro chemical studies such as potentiodynamic polarization and alternating current (AC) impedance have been used to find the mechanistic aspects of corrosion inhibition.

Self-passivation of austenitic steel 316 L and its welded joints in sulphuric acid

The spontaneous (self) – passivation and/or electrochemical passivation processes on austenitic steel 316 L and its welded joints were studied in deaerated sulphuric acid (1.7 M) at room temperature. Electrodes were prepared from materials taken from the central zone of the weld (zone 1), the so called overheated zone – OHZ (or temperature affected zone) (zone 2) and basic material – BM (zone 3). It has been concluded that the austenitic steel 316 L and its welded joints indicate the existence of self-passivation processes (passive corrosion) in deaerated sulphuric acid with formation of oxide-passive films (mainly Fe-Cr oxides) at the metal surface with thickness of 1-1.5 nm. As it was shown the corrosion behaviour of the welded material mainly depends on the chemical stability and the thickness of the passive film formed at the surfaces of the various zones. It can be also, concluded that the corrosion process is mainly located on the border of the fusion line OHZ-BM.

Analysis of nano film by atomic force microscopy

The corrosion inhibition efficiency of diethylenetriaminepenta(methylenephosphonic acid) (DTPMP) in combination with a bivalent cation like Zn2+ in controlling corrosion of mild steel immersed in rain water collected from rooftop, stored in concrete tank was investigated using weight loss method and electrochemical impedance spectroscopy. The combined corrosion inhibition efficiency offered by 50 ppm of DTPMP and 5 ppm of Zn2+ was 90 %. The synergistic effect of the inhibiting compound was calculated. The corrosion inhibition was observed due to the formation of more stable and compact protective film on the metal surface. Fluorescence spectral analysis was used in detecting the presence of an iron – inhibitor complex and the co-ordination sites of the metal inhibitor with iron were determined by the FTIR spectra. The surface morphology of the protective film on the metal surface was characterized by using atomic force microscopy (AFM).

Influence different chemical composition and percentage rate of added activators on depth of boride layer

During sintering and chemical-thermal treatment-boriding of samples from iron powder generates adequate boride layer, so in this paper are presented results of research dependence of depth of boride layer from composition of mixture which are used for boronizing process. Basic mixture used for boriding of investigated samples from iron powder is modified by addition of activators different chemical composition and in different percentage rate. The obtained boride layers vary in depth and quality (porosity, the contact with metal). In order to obtain better boride layers and to show certain appearances during boriding, it was necessary to choose mixture for boronising and to determine the most useful activators and their ratio. Processing of eksperimentaly obtained results is carried out by using Simplex method. Results of investigation and mathematical processing allow us to choose composition of mixture for boriding with depth change which is given in advance. It has been observed that simultaneously with boriding also sintering occured, and this fact offers a wide application possibility in the chemical-thermal treatment for sintered materials. It is possible to completely avoid sintering process of products wich are obtained with powder metallurgy.

This paper shows results of analysis of the kinetic model of different types of bauxite leaching by sodium-hydroxide. Different types of bauxite have been used: gibbsite, gibbsite-boehmite, boehmite, boehmite-diaspore and diaspore types of bauxite. After calculation of energy of activation, there has been considered correlation between energy of activation and the bauxite cell structure and derived appropriate models.

SOME ASPECTS OF COATINGS DELAMINATION

Ceramic coatings on the metal substrate create significiant stresses, when they start to cool down after the coating procedure. These stresses are the consequence of the mismatch in the thermal exspansion coefficients of the substrate and coating materials. One of the basic forms of these coatings destruction is the edge delamination. For the ideally brittle interface, the edge delamination of the compressed coating occurs as the Mode II interfacial fracture. In this paper shown that the fraction and roughness of the separated surfaces interface the fracture toughness. The proposed and analysed Mode II delamination in steady-state conditions enhances effects of friction and roughness between the coating and the substrate. This model in use in order to estimate which of the two effects is sufficient to explain the large value of the Mode II fracture toughness obtained in experiments. The model will be considered based on the interfacial fracture mechanics with programme package Mathematica.

CHARACTERIZATION OF SLUDGE FROM NEUTRALIZATION OF WASTE SOLUTIONS AND RINSING WATERS IN HOT DIP GALVANIZING PROCESSES

Sludge issued from waste water and spent solutions in hot dip galvanizing process pertains to hazardous industrial waste group. Managing of this type of waste is very complex and delicate. Initial step in managing of this specific waste is characterization. This paper presents Serbian regulative which is compatible with rules of European Directives in characterization of sludges.

BROJ 3

Desalination of brackish water using electrodialysis: Effect of operational conditions

As the most countries on the earth, shortage of drinking water is a major problem in Tunisia. One mean to obtain low cost drinking water is the desalination of brackish water. The desalination of brackish water by electrodialysis was investigated in this work. This technique is a membrane separation process based on the selective migration of aqueous ions through ion exchange membranes as a result of an electrical driving force. It represents one of the most important methods for desalting solutions as well as thermal process and reverse osmosis.
The parameters which can influence the performance of process were studied. These parameters are: concentration of feed solution, flow rate, voltage and circulation mode. Experiments were carried out on sodium chloride solutions with known concentration. Working in continuous mode showed that the desalination rate does not exceed 55%. However, working in batch recirculation mode, more efficient results were obtained. An initial concentration of 3 g L-1 of salts is considered as the maximum recommended feed concentration.

Strategy for the online monitoring of the Cr(VI) reduction

In this contribution, we describe an algorithm for the continuous monitoring of Cr(VI) occurring during a wastewater treatment. This approach performs its task having available only the online measurements of the redox potential. The results show that the redox potential is a valuable indicator of the process time evolution. The strategy here presented is based on the development of a mathematical model that includes online measurable states, with the property of being observable. Then, a sliding observer is designed for the estimation of Cr(VI). The paper includes the detailed design of the monitoring scheme as well as its experimental application at the laboratory level.

Corrosion behaviour of carbon steel in sodium nitrate solution

Corrosion behaviour of carbon steel in double distilled water, in the presence of various concentration of sodium nitrate (SN) have been evaluated by weight loss method, polarization study, AC impedance spectra, cyclic voltammetry, time vs current plots, and time vs potential plots. As the concentration of SN increases corrosion rate also increases. In the lower concentration regions (less than 500 ppm of SN) general corrosion takes place. Around 700 ppm of sodium nitrate (SN), SCC begins to start.

Nickel-diamond composite coatings are produced by electro deposition using sedimentation technique at various cathode current densities, pH and temperatures. Electro deposition was carried out from a conventional Watts bath. Natural diamond powder of 6-12 µm size was used. The hardness of depo-sited electro composites were measured using Vickers hardness measuring machine. A non linear regression equation was developed using 27 data obtained by designing an experiment with three level of experiment namely Low, Medium and High to predict the hardness of deposition in Ni-diamond metal matrix. Optimization of parameters of Ni-diamond composite coating such as pH, current density and temperature was done using a non traditional optimization technique called as Genetic Algorithm (GA). Within the range of input variables for the present case (pH = 2.5 to 4.5; current density (i) = 1 to 3 A/dm2 ; temperature = 30 to 600C), the optimized hardness was found to be 431.95 VHN at pH = 2.5 Current density (i) = 1 A/dm2and temperature = 300C.

When uncoated carbon steel was immersed in an aqueous solution containing 3.5% NaCl, there was corrosion of metal. But when nickel was electro deposited on carbon steel surface, corrosion protective efficiency was observed. The corrosion protective efficiency increased for the carbon steel, electroplated with nickel and chromium. The corrosion protective efficiency decreased for the carbon steel, electroplated with nickel – chromium – garlic extract. When 1% copper sulphate solution was placed on the uncoated carbon steel surface, the red color (Cu) started appearing in 65 seconds. But in the case of nickel – chromium – garlic deposited carbon steel surface, the reddish brown color did not appear even after 1200 seconds. Polarization study leads to the conclusion that when carbon steel is electroplated with nickel and chromium the metal surface becomes corrosion resistant and the resistance decreases when electroplated with garlic extract. AC impedance study leads to the conclusion that when carbon steel is electroplated with nickel and chromium the metal surface becomes corrosion resistant and the corrosion resistant decreases when electroplated with garlic extract. The decolourization study reveals that the nickel coated carbon steel was only 40% efficient in decolourizing methyl orange solution in chloride medium whereas, carbon steel coated with nickel – chromium was 95% efficient. When electroplating was done in the presence of garlic extract the decolourizing efficiency was 85%.

EFFECTS OF DIFFERENT MTBE CONCENTRATION ON SEED GERMINATION AND BIOMASS OF CORN (Zea mays), WHEAT (Triticum aestivum) AND ALFALFA (Medicagosativa)

MTBE was introduced in production in 1970`s in order to reduction of air pollution and replacing of toxic compounds from gasoline. After only a few years of its using, it becomes a one of important soil and water contaminant. The aim of this paper was investigation of seed germination and biomass of corn, wheat and alfalfa in presence of different MTBE concentration. The results of investigation showed the inhibitory MTBE effect on plant germination at all used concentration higher from 10 ppm. The decrease in plant biomass was more expressed in maize compared to other two species. It was concluded that MTBE due its mobility, solubility and persistence, had toxic effects on metabolic processes in seeds and changed biomass production in early stage of plant development.

Corrosion behaviour of carbon steel in river water in the presence of calcium propionate- Zn2+ system

The inhibition efficiency of calcium propionate (CP)-Zn2+ system in controlling corrosion of carbon steel in an aqueous environment has been evaluated by mass-loss method. A synergistic effect is noticed between calcium propionate and Zn2+.The formulation consisting of 50 ppm of calcium propionate and 50 ppm of Zn2+shows 91% inhibition efficiency (IE). At lower pH value IE decreases and in alkaline solution IE increases. Polarization study reveals that CP-Zn2+ system controls cathodic reaction predominantly. AC impedance spectra reveal that a protective film is formed on the metal surface. FTIR spectra reveal that the protective film consists of Fe2+-CP complex Zn(OH)2. and Ca(OH)2.

BROJ 4

Corrosion inhibition by monosodium glutamate-Zn2+ system

The inhibition efficiency of mono sodium glutamate (MSG)-Zn2+ system in controlling corrosion of carbon steel in an aqueous environment has been evaluated by mass- loss method. The synergistic effect is noticed between mono sodium glutamate and Zn2+. The formulation consisting of 100 ppm of mono sodium glutamate and 50 ppm of Zn2+ shows 86% inhibition efficiency(IE).At lower PH value IE decreases and in alkaline solution IE increases. Polarisation study reveals that MSG-Zn2+ system functions as a mixed inhibitor. AC impedance spectra reveal that a protective film is formed on the metal surface. FTIR spectra reveal that the protective film consists of Fe2+-MSG complex and Zn(OH)2.

Using pulse electrochemical polymerization technique we prepared high charge capacity polymer of 3, 4-Ethylenedioxythiophene (PEDOT) on glassy carbon (GC) substrate. The effect of pulse time on the growth processes and charge capacity of (PEDOT) has been investigated. Pulse on time plays an important role in controlling chain size and chain defects whereas pulse off time contributes in polymer conjugation and orientation. Stable PEDOT films with good electrochemical reversibility, high doping degree and high charge capacity were obtained by applying ultra short on time current pulse for polymerization. The characterization using scanning electron microscopy confirmed that the obtained PEDOT deposits were firstly formed as a thin layer followed by rough, nodular growth which produces an open and porous structure. A charge capacity up to 114 Fg-1 was obtained at time on of 10 ms.

Studies on the corrosion of welded areas of friction welded magnesium and its alloy AZ91D are done in view of their applications as structural materials in automotive and aerospace engineering. Friction welding of magnesium-magnesium, magnesium-AZ91D alloy and AZ91D alloy-AZ91D alloy is carried out at the welding speed of 600 RPM which produced a burn length of 2 mm. Corrosion of this welded area is studied using E-log I polarization in 0.1 M ammonium carbonate solution. It is found that the welded areas are more corrosion resistant than their respective parent samples under similar experimental conditions. Scanning electron microscopic images confirm the grain refinement of welded zones. For better understanding, E-log I polarization studies of pure magnesium and its alloy are also done.

Corrosion behavior of nickel and its alloys in HCl and its inhibition by natural rosemary oil

The corrosion behavior of nickel, Inconel 600 and Inconel 690 was studied in different concentrations of HCl solution and its inhibition by natural rosemary oil using galvanostatic polarization techniques. It was found that, HCl accelerate the corrosion of nickel and its alloys. The corrosion rate decreases in the following order Inconel 690 > Inconel 600 > Ni. This was attributed to the presence of high Cr content in the chemical composition of Inconel 690. Natural Rosemery oil inhibit the corrosion of nickel and its two alloys in 0.1 M HCl. The inhibition efficiency increases with increasing the concentration of this oil which act as an inhibitor of the mixed type. The inhibitive effect of this oil was explain in view of adsorption on the metal surface. The adsorption process follows Langmuir adsorption isotherm. The addition of this oil to the potentiodynamic anodic polarization curves of nickel and its two alloys in chloride solutions shift the pitting potential to more noble direction, indicating an increased resistance to pitting attack.

Preparation of new saturated polyamide compounds and its application as corrosion inhibitors for corrosion of carbon steel in hydrochloric acid solution

New one series of saturated polyamide was prepared by polycondensation of methylenedisalyclic acid (MDSA) with adipic acid and several diamine such as ethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentamine and pentaethylenehexamine. The structure of the prepared polyamide was detected by IR and 1H NMR spectra physical properties of these compounds were detected. These compounds were tested as a corrosion inhibitors for dissolution of carbon steel type (L-52) used in Egyptain petroleum pipe lines in 0.1M HCl solution using potentiodynamic polarization technique. The percentage inhibition efficiency increases with increasing the inhibitor concentration and number of amino group in the structure of polyamide. The inhibitive action of these compounds was explained in view of adsorption of these compounds on the surface of steel. The adsorption follows Langmuir adsorption process isotherm.

Corrosion inhibition by spirulina

An environmental friendly green inhibitor namely an aqueous extract of spirulina has been used to prevent the corrosion of carbon steel in aqueous solution containing 60 ppm of Cl – ion. Inhibition efficiencies of various concentrations of a 0.5% aqueous solution of spirulina have been evaluated by weight loss method and electrochemical studies such as polarization study and AC impedance spectra. As the concentration of spirulina increases, inhibition efficiency (IE) increases. As the value of pH increases, the IE of spirulina increases. As the duration of immersion increases, IE decreases. 6ml of spirulina solution offers inhibition efficiency greater than 80%. At pH 11 6ml of spirulina solution offers 90% corrosion inhibition efficiency. Electrochemical studies confirm the formation of a protective film on the metal surface.

THE WELDING SPECIFITY OF STEEL RESISTANCE TO CORROSION

In this paper the most important specifities of welding steel resistant to corrosion was given.The special view of their corrosion resistant , procedures for corrosion prevention and conditions at their welding was considered. Beside fundamental and specifities in view of corrosion behaviour, technology-metallurgically specifities which can be of practical importance at their exploatation in many industries sectors were given.
Through given analysis characteristics specificities tecnical-technological informations were given and these data can be of practical importance for engineering practice.